1. Field of the Invention
The present invention relates to a compressor and, more particularly, to the improved structure of a screw compressor where a motor rotor is secured and a compressor shaft runs stably.
2. Description of Related Art
FIG. 1 is a cross-sectional view illustrating a conventional screw compressor. The compressor comprises an electric motor 91 including a motor stator 93 and a motor rotor 94, a helical screw rotor 92, which are all accommodated in a housing 90. The housing 90 includes a housing body 901 and a housing cap 902, where the compressor is assembled in such a manner that the electric motor 91 and the helical screw rotor 92 are first installed in the housing body 901, and then the housing cap 902 is covered axially on an end of the housing body 901 for enclosing the same.
The helical screw rotor 92 is divided, in sequence from an end thereof near the electric motor 91, into a motor coupling section 921, a first supporting section 922, a helical screw section 923, and a second supporting section 924. The first and the second supporting sections 922, 924 are sleeved with a first bearing 95 and a second bearing 96, respectively. The motor coupling section 921 and the motor rotor 94 are coupled with each other and rotate synchronously together. The helical screw rotor 92 is pressed and stopped, at an end thereof, by a motor rotor stop 97, namely, via a fastening bolt passing through the motor rotor stop 97 and into the end of the helical screw rotor 92, so that the motor rotor stop 97 is secured on the helical screw rotor 92.
In conventional screw compressors, there are two types of design for helical screw rotor shafts: one is that the shaft has an end referring to the motor coupling section 921 and not exceeding an effective sensing section of the motor rotor 94, as shown in FIG. 1; the other one is that the motor coupling section 921 is extended for an additional section so as to exceed the effective sensing section of the motor rotor 94. Since vibration and displacement will inevitably occur for the shaft and the motor rotor 94 when the electric motor 91 rotates, in particular when the electric motor 91 rotates in a higher speed, the vibration and displacement will occur more seriously, making components of the compressor, such as bearings, damaged. Improvement to the compressor is thus demanded.